Ultrasound therapeutic and scanning apparatus

ABSTRACT

The present disclosure is directed to a precision ultrasound scanner for imaging, for example, the prostate in a way that produces a superior image of the prostate while removing the iatrogenic risk and patient discomfort associated with other methods of providing an ultrasound image of the prostate. The present disclosure describes an apparatus and method for forming a high precision image of the prostate from outside the patient&#39;s body wherein the resolution in sufficient to image, for example, cancerous lesions on the surface of the prostate. To achieve such images, coded excitation, tissue harmonic imaging, advanced transducers operating in the 10 MHz to 40 MHz range is used to achieve a useable signal-to-noise reflection while being able to position the imaging transducer as close as possible to the prostate without risk or discomfort to the patient. The present disclosure further discloses an imaging transducer and an irradiating therapeutic transducer can be mounted such that they are movable between a plurality of positions. The irradiating transducer is, for example, about a 12 MHz transducer with a focal length of about 20 mm to about 40 mm that would produce a strong second harmonic at about 24 MHz that could be used for imaging. The imaging transducer has, for example, a focal length of about 10 mm to about 20 mm and typically operates in the range of about 25 MHz to about 40 MHz.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/292,892 entitled “Ultrasound Scanning Apparatus” filed Oct.13, 2016, which claims the benefit of U.S. provisional patentapplication Ser. No. 62/240,636 entitled “Ultrasound Scanning Apparatus”filed Oct. 13, 2015. The entireties of the aforementioned applicationsare incorporated herein by reference.

FIELD OF INVENTION

The present disclosure relates to the use of ultrasound as anon-invasive means of both irradiating and imaging biological materialssuch the heart, liver, spleen and prostate and in particular directed toan apparatus for a low iatrogenic risk, easily implemented method forprecision ultrasound irradiating and imaging of the prostate gland.

BACKGROUND

Ultrasound imaging of body parts, including the eye has been pursued fora number of years. Ultrasound Bio Microscopy (UBMs) are hand-helddevices that have been available for years but are not suitable forprecision measurements. An arc scanner has been developed and tested forultrasound scanning of the eye under the names of Artemis 1, Artemis 2,Artemis 3 and the ArcScan Insight 100. These devices have given improvedultrasound scans of the eye by utilizing a precision registration systemand by using an eye seal to provide a continuous water (or waterequivalent) path from the transducer to the eye (the eye has acousticproperties similar to water).

The ArcScan Insight 100 can make B-scans of an eye with a resolution ofabout 30 microns and a repeatability of about 2 to 5 microns using asingle element transducer operating at a center frequency of about 40MHz. Other workers in the field have used lower frequency transducers inthe 5 to 10 MHz range to image the retina of an eye (the retina is onthe order of 25 mm from the anterior surface of the cornea). Others haveparticipated in work using annular array transducers and lineartransducer arrays as well as coded excitation techniques for imaging theeye and other body parts with ultrasound.

Many of the ArcScan Insight 100 hardware innovations (such fluidbearings and arc scanning with variable radii of curvature) and many ofthe well-known ultrasound image enhancement techniques (such as annulararray transducers, coded excitation, advanced data processing) can becombined to provide a precision ultrasound scanner for other body parts.

The prostate gland can be imaged by X-rays, MRI (magnetic resonanceimaging) or ultrasound. Imaging by ultrasound is non-ionizing and lessrisky than imaging by X-rays and is far more convenient than imaging byMRI.

Ultrasound imaging can be accomplished by a hand-held sector scannerdevice or by a trans-rectal ultrasound probe. The hand-held sectorscanner can make a qualitative image of the prostate by imaging throughthe abdominal wall but resolution is typically poor. This is a lowiatrogenic risk procedure and easily applied imaging technique but theimage quality is too poor to make informed decisions, for example aboutcancer cell development. The trans-rectal ultrasound probe can make abetter image than a hand-held sector scanner because the ultrasoundtransducer can be positioned within 10 or 20 millimeters of the prostategland on the other side of the rectal wall from the prostate. The imageis difficult to co-register successive B-scans and so is not quiteprecise and accurate enough to make informed decisions about, forexample, cancer cell development. In addition, a trans-rectal ultrasoundprobe causes some discomfort to the patient and has moderate iatrogenicrisk. The procedure can lead to infections if the endoscope isimproperly sterilized or more severe problems if the probe pierces therectal wall, as occasionally happens.

High-intensity focused ultrasound (HIFU) is a non-invasive therapeutictechnique that uses non-ionizing ultrasonic waves to heat tissue. HIFUcan be used to increase the flow of blood or to destroy tissue, such astumors, through a number of mechanisms. The technology is similar toultrasonic imaging, although practiced at lower frequencies and higheracoustic power. Acoustic lenses may be used to achieve the necessaryintensity at the target tissue without damaging the surrounding tissue.

A focused ultrasound system is used to treat essential tremor,neuropathic pain and Parkinsonian tremor. The focused ultrasoundapproach enables treatment of the brain without an incision orradiation. Treatment for symptomatic uterine fibroids became the firstapproved application of HIFU by the US Food and Drug Administration(FDA) in October 2004. Studies have shown that HIFU is safe andeffective, and that patients have sustained symptomatic relief issustained for at least two years without the risk of complicationsinvolved in surgery or other more invasive approaches.

HIFU has been successfully applied in treatment of cancer to destroysolid tumors of the bone, brain, breast, liver, pancreas, rectum,kidney, testes, prostate.

There remains a need for a low iatrogenic risk, easily implementedmethod of ultrasound irradiation and imaging for the prostate thatproduces a superior image that can be used as a screening tool andtreatment procedure for diseases of the prostate.

SUMMARY

These and other needs are addressed by the present disclosure. Thevarious embodiments and configurations of the present disclosure aredirected generally to ultrasound imaging of biological materials suchthe heart, liver, spleen and prostate and in particular directed to amethod and apparatus for a precision ultrasound scanning and treatmentof the prostate gland. The present disclosure describes two modes ofapplying ultrasound technology for both irradiating and imagingbiological materials such the heart, liver, spleen and prostate and inparticular directed to an apparatus for use in a non-invasive, lowiatrogenic risk method for precision ultrasound irradiating and scanningof the prostate and other organs.

In one mode, a high-intensity focused ultrasound source is used alongwith a higher frequency diagnostic ultrasound source to alternatelyprovide the required irradiating and then imaging capability through theperineum.

A system is disclosed for treating and imaging a body part of a patient,comprising a housing defining an enclosed volume, wherein the enclosedvolume is at least partially filled with a fluid. The system furtherincludes a transducer holder positioned in the fluid in the enclosedvolume of the housing, wherein the transducer holder is movable betweenor among a plurality of positions. The system further includes a firstultrasound transducer positioned on the transducer holder, wherein thefirst ultrasound transducer emits a first ultrasound wave in a firstfrequency range; a second ultrasound transducer positioned on thetransducer holder, wherein the second ultrasound transducer emits asecond ultrasound wave in a second frequency range. The first and secondfrequency ranges are distinct, and the transducer holder moves such thatone of the first or second ultrasound transducers is in an emissionposition of the plurality of positions to emit one of the first orsecond ultrasound waves, respectively, into a body part of a patient.

A method is disclosed for treating and imaging a body part of a patient,comprising providing a housing with an acoustically-transparent windowon a surface of the housing, wherein the housing is at least partiallyfilled with a fluid; and providing a first ultrasound transducer and asecond ultrasound transducer in the fluid in the housing, wherein thefirst ultrasound transducer emits a first ultrasound wave in a firstfrequency range, the second ultrasound transducer emits a secondultrasound wave in a second frequency range, and the first and secondfrequency ranges are distinct. The method further includes positioning apatient on the housing with a body part positioned over theacoustically-transparent window; emitting the first ultrasound wave fromthe first ultrasound transducer to image the body part of the patient;emitting the second ultrasound wave from the second ultrasoundtransducer to treat the body part of the patient; and emitting the firstultrasound wave from the first ultrasound transducer to re-image thebody part of the patient.

In a second mode, a high-intensity focused ultrasound source is usedalone and the detection of higher frequency harmonics by methodsgenerally known as tissue harmonic imaging are used to overcome highfrequency ultrasound attenuation and deliver the imaging resolutionrequired for screening and diagnosis.

This first mode of operation can be extended to include coded excitationand tissue harmonic imaging techniques to produce images at differentfrequencies and with two different focal length transducers. Thiscombination, for example, could be used to irradiate the target organwith non ionizing ultrasound while taking images of the target organ at12 MHz, 24 MHz, and 40 MHz.

A system is disclosed for treating and imaging a body part of a patient,comprising a housing defining an enclosed volume, wherein the enclosedvolume is at least partially filled with a fluid; anacoustically-transparent window on a surface of the housing; atransducer holder positioned in the fluid in the enclosed volume of thehousing; and a first ultrasound transducer positioned on the transducerholder, wherein the first ultrasound transducer emits a first ultrasoundwave at a first frequency in a first frequency range through theacoustically-transparent window and into a body part of a patient, andthe first ultrasound transducer receives a harmonic wave at a harmonicfrequency that is approximately twice the frequency of the firstfrequency from the body part of a patient after through theacoustically-transparent window.

In the present disclosure, known techniques can be combined in someembodiments to achieve high resolution and tissue depths of 60millimeters or more. These include the use of annular arrays of two ormore independent transducer elements; coded excitation of transmittedultrasound pulses; and detection of higher frequency harmonics inmethods generally known as tissue harmonic imaging.

An innovation of the present disclosure is the use of different types ofseating apparatuses that allow the use of a precision arc scanninginstrument to be used while minimizing or eliminating iatrogenic riskand patient discomfort. This approach provides for imaging and treatmentof the prostate gland from outside the body through the perineum so thatthe ultrasound probe or probes can get close to the prostate and avoidbony structures that would severely attenuate ultrasound energy.

The elements of a precision ultrasound scanning apparatus for imaging aprostate can include:

-   1. A scanning instrument container formed by a saddle (on which the    patient sits) and an instrument body under the saddle. The    instrument body contains the scanning apparatus and can be filled    with a liquid such as distilled water. Alternately, the scanning    instrument container can be formed by a bowl (on which the patient    sits) and an instrument body within the bowl. The instrument body    contains the scanning apparatus and wherein the instrument body can    be filled with a liquid such as distilled water.-   2. The scanning instrument container formed by a saddle can house    the scanning instrument and can also comprise stirrups for the    patient's feet, and handle bars. The stirrups and handle bars can    allow the patient to lean forward to assume an optimal position for    scanning.-   3. A scanning apparatus contained within the scanning instrument    container that can comprise an x-y-z-beta positioning mechanism; a    scan head that can comprise an arcuate guide track and/or a linear    guide track; a transducer probe carriage that moves along one of the    guide tracks; a transducer which can be a single element needle    probe, an annular array probe or a linear a transducer array. The    scanning apparatus can include a video camera that can provide an    optical image of the outside of the body part being scanned by the    ultrasound probe. The positioning mechanism may able to tilt the    scan head. Tilting means changing the tilt angle of the positioner    mechanism and scan head by rotating about the x-axis in the y-z    plane. The arcuate guide track is aligned with the x-axis such that    the transducer carriage moves back and forth in an arc aligned with    the x-axis. A linear guide track would also be aligned with the    x-axis such that the transducer carriage moves back and forth    parallel to the x-axis.-   4. A computer, comprising input and/or output devices that controls    the scanning apparatus (controls the positioning mechanism, the scan    head motion, the transmitting and receiving of the ultrasound probe    and the manipulation of A-scans to form a B-scan of the prostate    gland).-   5. A detachable window connected to and embedded in the saddle or    bowl of the scanning instrument container. The window is made from a    material that can transmit optical and acoustic energy. The window    may be round, elliptical or square with rounded corners such that    the window can allow the scanner to scan the selected body part of    the patient.-   6. A disposable and deformable container of clear gel that can    conform to the detachable window in the saddle and to the body part    being scanned by the ultrasound probe. For example, a disposable bag    of gel can be placed over the window. The patient sits on the bag so    that the gel is in contact with the window and with the patient's    body. Alternately, the disposable and deformable container could,    for example, be a pair of shorts with the disposable and deformable    container of clear gel sewn into the crotch area of the shorts.

The configuration of the scanning instrument container formed by asaddle or bowl on which the patient sits can allow the scan to beconducted upwards through the patient's perineum thereby providing ashort transmission/receiving path to the prostate while remaining anon-invasive procedure that minimizes patient discomfort and risk ofinfection. This configuration, as well as other configurationsdiscussed, are designed to 1) provide a continuous fluid path ofsubstantially similar acoustic transmission properties from theultrasound transducer to the body part being scanned and 2) minimize thedistance between the ultrasound transducer to the body part beingscanned.

In the example of the prostate gland, the frequency characteristic ofthe ultrasound probe and the peak power of the transducer emissions arecommonly selected so that an image of the prostate can be formed whenthe prostate is about 50 to 130 millimeters from the face of thetransducer element. The center frequency of the probe may be in therange of about 10 MHz to about 40 MHz to provide the required imageresolution.

The peak power output of the ultrasound probe will be within the limitsestablished by the FDA or other regulatory body. For example, aspatial-peak pulse-average intensity of 94 mW/cm² and a spatial-peaktemporal-average intensity of 190 W/cm2 would be allowable under 2008FDA guidelines (Publication Reference 4) for the prostate gland. Thiscompares to a spatial-peak pulse-average intensity of 17 mW/cm² and aspatial-peak temporal-average intensity of 28 W/cm2 allowable undercurrent FDA guidelines for ophthalmic imaging. This represents asix-fold increase in transducer power over allowable ophthalmic imagingtransducer power (a scan depth of about 6 to 7.5 mm for anterior segmentscanning of the human eye and a scan depth of about 25 mm for retinalscanning of the human eye).

It is noted that attenuation of signal strength in body tissue istypically about 0.5 dB per cm per MHz.

The present disclosure can utilize annular array transducers to increasethe depth of tissue that can be scanned since annular array transducerscan transmit at its characteristic frequency and receive at thecharacteristic frequency or at twice the characteristic frequency.

The present disclosure can also utilize coded excitation techniques suchas chirp-coded excitation or Golay code excitation, for example, andover-sampling techniques to increase signal-to-noise ratio therebyallowing deeper imaging capability. As in the ultrasound devicedescribed herein for scanning the eye, the noise floor of the dataacquisition system is typically the noise figure associated with theamplifier input to the A/D device.

The method of the present disclosure using the above described saddle orbowl apparatus can include the following steps:

-   1. The scanning instrument container is filled with distilled water-   2. The disposable and deformable container of clear gel is placed on    the saddle and the patient sits on the container of clear gel in    preparation for scanning. Alternately, the patient puts on the    disposable shorts and sits on the saddle or bowl.-   3. When the probe is centered on the arcuate guide track, the video    camera is used to position the ultrasound probe on the area of    interest of the patient. In this operation, the positioner assembly    moves the scan head into position for scanning.-   4. Scans are then made at different depths of focus and at different    meridians by:-   $ aligning the arcuate guide track by rotating the arcuate guide    assembly about its beta axis-   $ translating the scan head by small amounts-   $ tilting the scan head assembly by small amounts

The above general procedure can be similar to that used for ultrasoundscanning of an eye using an arc scanning device. The above scanningmodes are discussed in further detail in FIGS. 9A-9F.

The following definitions are used herein:

The phrases at least one, one or more, and and/or are open-endedexpressions that are both conjunctive and disjunctive in operation. Forexample, each of the expressions “at least one of A, B and C”, “at leastone of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B,or C” and “A, B, and/or C” means A alone, B alone, C alone, A and Btogether, A and C together, B and C together, or A, B and C together.

Acoustic impedance means the product of sound speed times density, ρc,where ρ is the density (˜993 kg/cu meter for water at 37 C) and c is thesound speed (1,520 meters per second at 37 C). Thus acoustic impedanceof water at 37 C is about 1.509×10⁶ kg/(sq meter-sec) or 1.509 Mrayls.

An acoustically reflective surface or interface is a surface orinterface that has sufficient acoustic impedance difference across theinterface to cause a measurable reflected acoustic signal. A specularsurface is typically a very strong acoustically reflective surface.

Anterior means situated at the front part of a structure; anterior isthe opposite of posterior.

An A-scan is a representation of a rectified, filtered reflectedacoustic signal as a function of time, received by an ultrasonictransducer from acoustic pulses originally emitted by the ultrasonictransducer from a known fixed position relative to a body component.

Accuracy as used herein means substantially free from measurement error.

Aligning means positioning the acoustic transducer accurately andreproducibly in all three dimensions of space with respect to a featureof the body component of interest (such as the heart, liver, spleen andprostate, etcetera).

An arc scanner, as used herein, is an ultrasound eye scanning devicewhere the ultrasound transducer moves back and forth along an arcuateguide track wherein the focal point of the ultrasound transducer istypically placed somewhere within the eye near the region of interest(i.e. the corneas, the lens etcetera). The scanner may also include alinear guide track which can move the arcuate guide track laterally suchthat the effective radius of curvature of the arcuate track is eitherincreased or decreased. The scanner utilizes a transducer that bothsends and receives pulses as it moves along 1) an arcuate guide track,which guide track has a center of curvature whose position can be movedto scan different curved surfaces; 2) a linear guide track; and 3) acombination of linear and arcuate guide tracks which can create a rangeof centers of curvature whose position can be moved to scan differentcurved surfaces.

Automatic refers to any process or operation done without material humaninput when the process or operation is performed. However, a process oroperation can be automatic, even though performance of the process oroperation uses material or immaterial human input, if the input isreceived before performance of the process or operation. Human input isdeemed to be material if such input influences how the process oroperation will be performed. Human input that consents to theperformance of the process or operation is not deemed to be “material.”

Auto-centering means automatically, typically under computer control,causing centration of the arc scanning transducer with the bodycomponent of interest.

Body habitus is somewhat redundant, since habitus by itself means“physique or body build.”. Body size and habitus describe the physicalcharacteristics of an individual and include such considerations asphysique, general bearing, and body build.

A B-scan is a processed representation of A-scan data by either or bothof converting it from a time to a distance using acoustic velocities andby using grayscales, which correspond to A-scan amplitudes, to highlightthe features along the A-scan time history trace (the latter alsoreferred to as an A-scan vector).

Centration means substantially aligning the center of curvature of thearc scanning transducer in all three dimensions of space with the centerof curvature of the eye component of interest (such as the cornea,pupil, lens, retina, etcetera) such that rays from the transducer passthrough both centers of curvature. A special case is when both centersof curvature are coincident.

Coded excitations are engineered excitation pulses that are capable ofincreasing the effective penetration depth of a transmitted signal inecho location imaging systems such as radar, sonar and ultrasound, byimproving the signal-to-noise ratio (SNR).

Chirping is a coded excitation that can be thought of as a complexexponential sequence with linearly increasing frequency. A linear chirpis a coded signal that linearly spans a frequency bandwidth B=f₂−f₁,where f₁ and f₂ are the starting and ending frequencies, respectively.If the chirp sweeps from f₁ to f₂ over a time, then the chirp-codedexcitation is described by: s(t)=ω(t) cos(2πf₁t+πbt²).

Fiducial means a reference, marker or datum in the field of view of animaging device.

Fixation means having the patient focus an eye on an optical target suchthat the eye's optical axis is in a known spatial relationship with theoptical target. In fixation, the light source is axially aligned in thearc plane with the light source in the center of the arc so as to obtainmaximum signal strength such that moving away from the center of the arcin either direction results in signal strength diminishing equally ineither direction away from the center.

A guide is an apparatus for directing the motion of another apparatus.

Hand-held ultrasonic scanner See Ultrasound Bio Microscopy (UBM).

HIFU Means High-Intensity Focused Ultrasound.

The home position of the imaging ultrasound transducer is its positionduring the registration process.

An iatrogenic risk is a risk due to the activity of a physician orsurgeon or by medical treatment or diagnostic procedures. For example,an iatrogenic illness is an illness that is caused by a medication orphysician.

An imaging ultrasound transducer is the device that is responsible forcreating the outgoing ultrasound pulse and detecting the reflectedultrasound signal that is used for creating the A-Scans and B-Scans.

As used herein, a meridian is a 2-dimensional plane section through theapproximate center of a 3-dimensional eye and its angle is commonlyexpressed relative to a horizon defined by the nasal canthus andtemporal canthus of the eye.

A medical procedure is defined as non-invasive when no break in the skinis created and there is no contact with the mucosa, or skin break, orinternal body cavity beyond a natural or artificial body orifice.Non-invasive procedures include specialized forms of surgery, such asradio surgery. extra corporeal shock wave lithotripsy (using an acousticpulse for treatment of stones in the kidney, gallbladder or liver forexample),

The perineum is the pelvic floor and associated structures occupying thepelvic outlet, bounded anteriorly by the pubic symphysis, laterally bythe ischial tuberosities, and posteriorly by the coccyx. The regionbetween the scrotum and the anus in males,

Positioner means the mechanism that positions a scan head relative to aselected part of an eye. In the present disclosure, the positioner canmove back and forth along the x, y or z axes and rotate in the βdirection about the z-axis. Normally the positioner does not move duringa scan, only the scan head moves. In certain operations, such asmeasuring the thickness of a region, the positioner may move during ascan.

Position tracking sensors are a set of position sensors whose solepurpose is to monitor the movement of the eye or any other anatomicalfeature during the imaging scan so as to remove unwanted movement of thefeature.

Posterior means situated at the back part of a structure; posterior isthe opposite of anterior.

Precise as used herein means sharply defined and repeatable.

Precision means how close in value successive measurements fall whenattempting to repeat the same measurement between two detectablefeatures in the image field. In a normal distribution precision ischaracterized by the standard deviation of the set of repeatedmeasurements. Precision is very similar to the definition ofrepeatability.

The prostate is a compound tubuloalveolar exocrine gland of the malereproductive system. The function of the prostate is to secrete aslightly alkaline fluid, milky or white in appearance, that in humansusually constitutes roughly 30% of the volume of the semen

The pulse transit time across a region of the eye is the time it takes asound pulse to traverse the region.

A pulser/receiver board carries the electronics required 1) to shape theelectrical pulse to drive the ultrasound transducer; 2) to receive thereturn signal from the ultrasound pulse engaging the target; and 3) toisolate the stronger driver pulse from the much weaker received pulse.

Refractive means anything pertaining to the focusing of light rays bythe various components of the eye, principally the cornea and lens.

Registration as used herein means aligning.

Scan head means the mechanism that comprises the ultrasound transducer,the transducer holder and carriage as well as any guide tracks thatallow the transducer to be moved relative to the positioner. Guidetracks may be linear, arcuate or any other appropriate geometry. Theguide tracks may be rigid or flexible. Normally, only the scan head ismoved during a scan.

Sector scanner is an ultrasonic scanner that sweeps a sector like aradar. The swept area is pie-shaped with its central point typicallylocated near the face of the ultrasound transducer.

A specular surface means a mirror-like surface that reflects eitheroptical or acoustic waves. For example, an ultrasound beam emanatingfrom a transducer will be reflected directly back to that transducerwhen the beam is aligned perpendicular to a specular surface.

Swept beam liquid interface ultrasound technology is an ultrasoundtechnology wherein the transducer is moved in a prescribed path duringscanning and wherein the ultrasound beam travels through a liquid mediumfrom transducer face to the tissue being imaged. Swept beam liquidinterface ultrasound technology is distinct from array based ultrasoundtechnology.

Tissue means an aggregate of cells usually of a particular kind togetherwith their intercellular substance that form one of the structuralmaterials of a plant or an animal and that in animals include connectivetissue, epithelium, muscle tissue, and nerve tissue.

A track or guide track is an apparatus along which another apparatusmoves. In an ultrasound scanner or combined ultrasound and opticalscanner, a guide track is an apparatus along which one or moreultrasound transducers and/or optical probes moves during a scan.

Trans-rectal ultrasound is used to create an image of organs in thepelvis by a probe inserted into the rectum. The most common usage fortransrectal ultrasound is for the evaluation of the prostate gland inmen with elevated prostate specific antigen or prostatic nodules ondigital rectal exam.

Tissue harmonic imaging exploits non-linear propagation of ultrasoundthrough the body tissues. The high pressure portion of the wave travelsfaster than low pressure resulting in distortion of the shape of thewave. This change in waveform leads to generation of harmonics(multiples of the fundamental or transmitted frequency) from tissue.Typically, the 2nd harmonic is used to produce the image as thesubsequent harmonics are of decreasing amplitude and hence insufficientto generate a proper image. These harmonic waves that are generatedwithin the tissue, increase with depth to a point of maximum intensityand then decrease with further depth due to attenuation. Hence themaximum intensity is achieved at an optimum depth below the surface.Advantages over conventional ultrasound include: decreased reverberationand side lobe artifacts; increased axial and lateral resolution;increased signal to noise ratio; and improved resolution in patientswith large body habitus.

Ultrasonic or ultrasound means sound that is above the human ear's upperfrequency limit. When used for imaging an object like the eye, the soundpasses through a liquid medium, and its frequency is many orders ofmagnitude greater than can be detected by the human ear. Forhigh-resolution acoustic imaging in the eye, the frequency is typicallyin the approximate range of about 5 to about 80 MHz.

Ultrasound Bio Microscopy (UBM) is an imaging technique using hand-heldultrasound device that can capture anterior segment images using atransducer to emit short acoustic pulses ranging from about 20 to about80 MHz. This type of ultrasound scanner is also called a sector scanner.The UBM method is capable of making qualitative ultrasound images of theanterior segment of the eye but cannot unambiguously make accurate,precision, comprehensive, measurable images of the cornea, lens or othercomponents of the eye.

A vector refers to a single acoustic pulse and its multiple reflectionsfrom various eye components. An A-scan is a representation of this datawhose amplitude is typically rectified.

Water equivalent as used herein means a fluid or a gel having theapproximate acoustic impedance of water.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may take form in various components andarrangements of components, and in various steps and arrangements ofsteps. The drawings are only for purposes of illustrating the preferredembodiments and are not to be construed as limiting the disclosure. Inthe drawings, like reference numerals may refer to like or analogouscomponents throughout the several views.

FIG. 1 is a schematic of a prior art arc scanner for imaging an eyeusing ultrasound.

FIGS. 2A and 2B are schematics of prior art single and dual elementultrasound transducer assemblies.

FIG. 3 is a schematic of the transducer face of a prior artmulti-element ultrasound transducer configuration.

FIG. 4 is an example of a simple emitted and received ultrasound pulsewaveform.

FIG. 5 shows examples of several known emitted chirp ultrasound pulsewaveforms.

FIG. 6 illustrates the male perineum and the direction of the transducerpulse of the present disclosure.

FIGS. 7A-7C are schematics of a saddle seating apparatus with anultrasound scanner inside.

FIGS. 8A-8C are schematics of a bowl seating apparatus with anultrasound scanner inside.

FIGS. 9A-9F illustrates modes of positioning a scan head with respect toa patient.

FIG. 10 illustrates the co-ordinate system used by the scanning devicesof the present disclosure.

FIG. 11 is a schematic of a bowl seating apparatus with an ultrasoundscanner inside and a patient in position for scanning the prostate.

FIGS. 12A and 12B are schematics of a revolver type swept beamtransducer holder.

DETAILED DESCRIPTION OF THE DRAWINGS

In this disclosure, an apparatus and a method are described that are thebasis for a rapid screening device for non-invasive, high qualityimaging and treatment of the prostate. This method can also be appliedto other body parts. The apparatus and method combine several knownultrasound imaging components and techniques such as precision eyescanners, annular array transducers, coded excitation and biharmonictissue imaging in an innovative way to ensure high quality imaging andpatient comfort and safety. An important aspect of this disclosure isthe apparatus and method to position the patient and the scanningapparatus in a way that minimizes the transducer distance to theprostate gland while preserving patient comfort and minimizing oreliminating patient risk.

Precision Eye Scanner

An ultra sound scanning apparatus, as described for example, in U.S.Pat. No. 8,317,709 is comprised of a positioning mechanism and a scanhead. The positioning mechanism has x, y, z and beta (rotation about itsz-axis) positioning mechanisms which make it possible to position thescan head relative to the eye component of interest. This operation iscarried out while the patient's eye is positioned in contact with aneyepiece attached to the scanner and while the patient's head is fixedrelative to the scanner by a head rest or by the eyepiece or by acombination of both. Once the positioning mechanism is set, the onlymoving part relative to the eye component of interest is the scan head.The scan head may be comprised of only an arcuate guide track which istypically used to produce an ultrasound scan of the cornea and/or muchof the anterior segment of an eye. The scan head may be comprised ofonly a linear guide track. In another embodiment, the scan head may becomprised of an arcuate guide track and a linear guide track that can bemoved in a combination of linear and arcuate motions to produce anultrasound scan of the entire anterior segment including much of theposterior surface of the lens. The movement of the positioner and scanhead relative to patient's eye socket is precisely known at all times bya system of magnetic encoder strips.

The movement of the scan head relative to the eye component of interestis therefore known with precision and accuracy as long as the patientdoes not move their eye during the scan. A single scan can take lessthan a second. A sequence of scans can take several seconds. A patient'seye can move significantly even during a single scan, thus degrading theprecision and accuracy of the scan. The usual procedure, when thisoccurs, is to re-scan the patient. In US Publication No. 20130310692entitled “Correcting for Unintended Motion for Ultrasonic Eye Scans”, adevice and method of tracking any movement of the patient's eye,relative to the positioning mechanism, during a scan is described.

Ultrasound Eye Scanning Apparatus

FIG. 1 is a schematic of the principal elements of a prior artultrasound eye scanning device such as described in U.S. Pat. No.8,510,883. The scanning apparatus 101 of this example is comprised of ascan head assembly 108 (shown here as an arcuate guide 102 with scanningtransducer 104 on a transducer carriage which moves back and forth alongthe arcuate guide track, and a linear guide track 103 which moves thearcuate guide track back and forth as described in FIG. 4), apositioning mechanism 109 comprised of an x-y-z and beta mechanisms 105mounted on a base 106 which is rigidly attached to scanning apparatus101, and a disposable eyepiece 107. The scanning machine 101 istypically connected to a computer (not shown) which includes a processormodule, a memory module, and a video monitor. The patient is seated atthe machine 101 with their eye engaged with disposable eyepiece 107. Thepatient is typically looking downward during a scan sequence. Thepatient is fixed with respect to the scanning machine 101 by a headrestsystem and by the eyepiece 107. The operator using, for example, a mouseand/or a keyboard and video screen inputs information into the computerselecting the type of scan and scan configurations as well as thedesired type of output analyses. The operator, for example, again usinga mouse and/or a keyboard, a video camera located in the scanningmachine and video screen, then centers a reference marker such as, forexample, a set of cross hairs displayed on a video screen on the desiredcomponent of the patient's eye which is also displayed on video screen.This is done by setting one of the cross hairs as the prime meridian forscanning. These steps are carried out using the positioning mechanismwhich can move the scan head in the x, x, z and beta space (threetranslational motions plus rotation about the z-axis). Once this isaccomplished, the operator instructs computer using either a mouseand/or a keyboard to proceed with the scanning sequence. Now thecomputer processor takes over the procedure and issues instructions tothe scan head 108 and the transducer 104 and receives positional andimaging data. The computer processor proceeds with a sequence ofoperations such as, for example: (1) with the transducer carriagesubstantially centered on the arcuate guide track, rough focusing oftransducer 104 on a selected eye component; (2) accurately centering ofthe arcuate guide track with respect to the selected eye component; (3)accurately focusing transducer 104 on the selected feature of theselected eye component; (4) rotating the scan head through a substantialangle (including orthogonal) and repeating steps (1) through (3) on asecond meridian; (5) rotating the scan head back to the prime meridian;(6) initiating a set of A-scans along each of the of selected scanmeridians, storing this information in the memory module; (7) utilizingthe processor, converting the A-scans for each meridian into a set ofB-scans and then processing the B-scans to form an image associated witheach meridian; (8) performing the selected analyses on the A-scans,B-scans and images associated with each or all of the meridians scanned;and (9) outputting the data in a preselected format to an output devicesuch as storage disk drive or a printer. As can be appreciated, thepatient's head must remain fixed with respect to the scanning machine101 during the above operations when scanning is being carried out,which in a modern ultrasound scanning machine, can take several tens ofseconds.

An eyepiece serves to complete a continuous acoustic path for ultrasonicscanning, that path extending in water from the transducer to thesurface of the patient's eye. The eyepiece 107 also separates the waterin which the patient's eye is immersed from the water in the chamber inwhich the transducer guide track assemblies are contained. The patientsits at the machine and looks down through the eyepiece 107 as shown byarrow 110. Finally, the eyepiece provides an additional steady rest forthe patient and helps the patient to remain steady during a scanprocedure.

As can be appreciated, the arcuate guide track used to image the eye hasa radius of curvature similar to that of the cornea and anterior surfaceof the natural lens. If an arcuate guide track is used for imaging aprostate, for example, the radius of curvature can be appropriatelyadjusted by a combination of arcuate and linear motions such asdescribed for example in U.S. Pat. No. 8,317,709. As can be furtherappreciated, the guide track can have another shape than arcuate orcould, in principle, be made to flex in a precise way so as to customfit a patient.

Annular Array Transducers, Coded Excitation and Tissue Harmonic Imaging

Single Element Ultrasound Transducer

A prior art single element or needle transducer is shown in FIG. 2a(taken from a slide show entitled “Ultrasound Transducers” by RaviManaguli). This type of transducer is currently used in precision arcscanners such as described in FIG. 1, in the previous section and, forexample, in U.S. Pat. Nos. 8,317,702 and 8,758,252. The singletransducer element both transmits an ultrasound pulse and receives theechoed pulse.

Annular Array Ultrasound Transducers

FIG. 2b is a schematic of a prior art dual element ultrasound transducerassembly as described in “20 MHz/40 MHz Dual Element Transducers forHigh Frequency Harmonic Imaging”, Kim, Cannata, Liu, Chang, Silvermanand Shung, IEEE Transactions on Ultrasonics, Ferroelectrics andFrequency Control, VOL. 55; NO. 12, December 2008. Both the annularelement and the center element can transmit and receive ultrasoundpulses independently. In another mode, the center element can transmitand receive a pulse at one frequency while the annular element cantransmit and receive a separate pulse at a different frequency. In yetanother mode, the annular element can transmit and receive a pulse atone frequency while the center element can receive the echoed pulse at aharmonic frequency of the transmitted pulse.

As discussed in the above reference, a concentric annular type dualelement transducer was used for second harmonic imaging to improvespatial resolution and depth of penetration for ophthalmic imagingapplications. The outer ring element was designed to transmit a 20 MHzsignal and the inner circular element was designed to receive the 40 MHzsecond harmonic signal.

Tissue harmonic ultrasound imaging has been accepted as one of thestandard imaging modalities in many applications since its introductionto medical ultrasound imaging in the 1990 s. Especially in cardiac andabdominal studies, tissue harmonic imaging is very often used fordiagnostics along with fundamental imaging. By utilizing the secondharmonic component of the received signal, images can be improved byreducing near field reverberation, decreasing phase aberration error,and improving border delineation.

In ophthalmology, imaging of the posterior segment which includes theretina, require improved spatial resolution and depth of penetration forproper diagnosis of retinal disease. This same second harmonic imagingtechnique can be used to improve imaging of, for example, the prostate.

Recently, broad band single element transducers operating at about 20MHz have been used for imaging the posterior segment of the eye, butwere limited in spatial resolution at that frequency. Unfortunately,transducers operating at 20 MHz cannot provide the spatial resolutionneeded to adequately delineate layers on the posterior segment of thehuman eye. Those operating in the higher frequency range do not providesufficient depth of penetration such that the reflected signal can bedetected above the noise floor. A concentric annular type dual elementtransducer for second harmonic imaging of the posterior segment of theeye wherein the outer ring element is used for transmit and the innercircular element for receive. A ring-shaped outer element produceshigher side lobes than does a circular element of the same diameter, butthis is to some degree compensated for by inherently lower side lobes inthe harmonic compared with the fundamental.

Harmonic imaging with 20 MHz transmit and 40 MHz receive showedcapability superior to that of fundamental imaging at 20 MHz to diagnoseretinal disease in the posterior segment of the eye. The centerfrequencies of transmit and receive elements of dual element transducerscan be further optimized to match the designed center frequencies tosupport a larger dynamic range. The aperture size of transmit andreceive elements can also be optimized with further experimentation toachieve the best combination of transmit and receive efficiency.

There is a need to form a high precision image of the prostate fromoutside the patient's body wherein the resolution in sufficient toimage, for example, cancerous lesions on the surface of the prostate. Toachieve such images, coded excitation, tissue harmonic imaging, advancedtransducers operating in the 10 MHz to 20 MHz range will be required toachieve a useable signal-to-noise reflection while being able toposition the imaging transducer as close as possible to the prostatewithout risk or discomfort to the patient.

FIG. 3 is a schematic of the transducer face of a prior artmulti-element ultrasound transducer configuration (taken from a slideshow entitled “Ultrasound transducers by Ravi Managuli).

As discussed in “High-Frequency Ultrasonic Imaging of the AnteriorSegment Using an Annular Array Transducer” Ronald H. Silverman, JeffreyA. Ketterling and D. Jackson Coleman, Ophthalmology. April 2007,very-high-frequency ultrasound (VHFU>35 MHz) allows imaging of anteriorsegment structures of the eye with a resolution of less than 40 microns.The low focal ratio of VHFU transducers, however, results in adepth-of-field of less than 1,000 microns (1,000 microns is equal to1-mm). A dual element high-frequency annular array transducer for ocularimaging shows improved depth-of-field sensitivity and resolutioncompared to conventional single element transducers.

As also discussed in the preceding reference, a spherically curvedmultiple annular array ultrasound transducer was tested wherein thearray consisted of five concentric rings of equal area, had an overallaperture of 6 mm and a geometric focus of 12 mm. The nominal centerfrequency of all array elements was 40 MHz. An experimental system wasdesigned in which a single array element was pulsed and echo datarecorded from all elements. By sequentially pulsing each element, echodata were acquired for all 25 transmit/receive annular combinations. Theecho data were then synthetically focused and composite images produced.This technology offers improved depth-of-field, sensitivity and lateralresolution compared to single element fixed focus transducers and dualelement annular array transducers currently used for VHFU imaging of theeye.

Factors that impact upon the overall utility of ultrasound systemsinclude resolution, penetration, speed (frames/second), sensitivity(signal/noise) and depth-of-field. Resolution generally improves (andpenetration declines) with frequency. Very-high-frequency (>35 MHz)ultrasound (VHFU) provides an axial resolution of <40-μm, allowingexquisitely detailed depiction of anatomic structures. However,attenuation at this frequency is high, even in water, limiting clinicalimaging in this frequency range to the anterior segment.

Annular arrays can be fabricated with no curvature (i.e., flat) with aspherical lens, or with a spherical geometry. While the principle ofdynamic focusing is the same for all, spherically curved devices areadvantageous compared to flat arrays because fewer elements are requiredto achieve the same improvement in depth of field. Spherical curvaturealso leads to better lateral resolution for two transducers of similaraperture and number of elements.

Current VHFU systems for evaluation of the anterior segment of the eyeare constrained by their very limited depth of field. This results inreduced sensitivity and degraded resolution outside a focal zone thatmeasures under one millimeter in axial extent. The performance of anannular array transducer operating in the same frequency range ascurrent single-element UBM systems showed that this technology canprovide a six-fold increase in depth of field. The improved resolutionand sensitivity offered by annular array technology can thereforeprovide significant practical advantages in diagnostic imaging ofanatomy and pathology. Furthermore, this technology can be readilyextended to lower frequencies, such as 20-25 MHz, that would allowimproved assessment of pathologies. In summary, a 40-MHz multipleannular array transducer for imaging of the anterior and posteriorsegments can be fabricated to achieve improved depth-of-field,sensitivity and lateral resolution.

Spatial resolution in an ultrasonic imaging system is dependent on beamand focal properties of the source, tissue attenuation, non-linearity ofthe medium, tissue inhomogeneity, and speed of sound speed in eachtissue region.

In ultrasound, axial resolution is improved as the bandwidth of thetransducer is increased, which typically occurs for higher centerfrequencies. However, the attenuation of sound typically increases asfrequency increases, which results in a decrease in penetration depth.Therefore, there is an inherent tradeoff between spatial resolution andpenetration in ultrasonic imaging.

One way to increase the penetration depth without reducing axialresolution is by increasing the excitation pulse amplitude. However,increased excitation amplitude results in increased pressure levels thatcould result in unwanted heating or damage to tissues. Therefore,increasing the excitation pulse amplitude is not always a viablesolution, depending on the region being imaged. For example, regulationsfor ultrasound power and time duration are low for the eye relative tothe heart.

Coded Excitation

Coded excitations are engineered excitation pulses that are capable ofincreasing the effective penetration depth of a transmitted signal inecho location imaging systems such as radar, sonar and ultrasound, byimproving the signal-to-noise ratio (SNR).

An alternate solution to increase the penetration depth, as opposed toincreasing the excitation pulse amplitude, would be to increase theexcitation pulse duration by using coded excitation which increases thetotal transmitted energy and allows for the minimization of thetransmitted peak power. However, increasing signal duration has thenegative effect of decreasing the axial resolution of the ultrasonicimaging system.

In order to restore the axial resolution after excitation with a codedsignal, pulse compression is used. Pulse compression can be realized byusing one or more filtering methods. The main disadvantage of usingcoded excitation and pulse compression would be the introduction ofrange side lobes that can appear as false echoes in an image. Theintroduction of range side lobes is a detriment to ultrasonic imagequality because it can reduce the contrast resolution. The mainadvantage for using coded excitation is that it is known to improve theecho signal-to-noise ratio by increasing the time/bandwidth product ofthe coded signal. This improvement in echo signal-to-noise results ingreater depth of penetration in the range of a few centimeters forultrasonic imaging and improved image quality. Furthermore, thisincrease in penetration depth allows the possibility of shifting tohigher frequencies with larger bandwidths in order to increase thespatial resolution at depths where normally it would be difficult toimage.

Ultrasound is a non-ionizing, non-invasive, real-time imaging methodthan other techniques such as magnetic resonance imaging. However, thefiner resolution advantages offered by high frequency ultrasound areoffset by limitations in penetration depth caused by frequency-dependentattenuation and limitations in depth-of-field when low f-numbertransducers are employed to improve cross-range resolution. Attenuationof ultrasound in tissue increases with frequency and, therefore, currentuses of high frequency ultrasound are limited to applications that donot require deep penetration to image the tissue of interest. Highfrequency ultrasound image quality can be significantly improved byusing two independent approaches.

The first approach uses synthetic focused annular arrays with overallapertures similar to typical spherically focused transducers to increasedepth-of-field. The radial symmetry of annular arrays leads to ahigh-quality radiation pattern while employing fewer elements thanlinear or phased arrays. However, annular arrays need to be mechanicallyscanned to obtain a 2D image.

An annular array ultrasound transducer can consist of a two elementarray such as shown in FIG. 2b or a multi-element array such as shown inFIG. 3.

As an example, concentric annular type dual element transducers forsecond harmonic imaging at 20 MHz/40 MHz were designed to improvespatial resolution and depth of penetration for ophthalmic imagingapplications. The outer ring element may be designed to transmit the 20MHz signal and the inner circular element may be designed to receive the40 MHz second harmonic signal. These types of annular arrays aredescribed, for example, in “20 MHz/40 MHz Dual Element Transducers forHigh Frequency Harmonic Imaging, Kim, Cannata, Liu, Chang, Silverman andShung, IEEE Transactions on Ultrasonics, Ferroelectrics and FrequencyControl, Vol. 55; NO. 12, December 2008.

A multi-annuli array transducer is described in “Chirp Coded ExcitationImaging with a High-frequency Ultrasound Annular Array”, Mamou,Ketterling and Silverman, IEEE Trans Ultrasonics, Ferroelectrics andFrequency Control. 28 Feb. 2008. The array consists of five equal-areaannuli with a 10-mm total aperture and a 31-mm geometric focus.

The second high frequency ultrasound imaging approach uses codedexcitations (i.e., engineered excitation pulses) that are capable ofincreasing the effective penetration depth by improving thesignal-to-noise ratio. Resolution and penetration depth are criticallyimportant for medical ultrasound imaging. Normally, these two propertiespresent a tradeoff, in which one property can be improved only at theexpense of the other. However, it has been demonstrated that codedexcitation is capable of extending the limit associated with thistradeoff. Coded excitation permits the signal-to-noise ratio to beincreased through appropriate encoding on transmit and decoding onreceive. In a published study, linear chirp signals were used to excitean annular array transducer. The objectives of this study were todemonstrate that chirp annular array imaging can lead to better imagequality than current state-of-the-art high frequency ultrasound images.The described methods are general and are applicable to a vast range ofclinical applications, including ophthalmological, dermatological, andgastrointestinal imaging.

To appreciate how coded excitation can increase signal-to-noise ratio(SNR), white noise can be added to the received response. Typically, aresponse had an SNR of 45 dB, which is in the range of most ultrasoundimaging systems. Chirp excitations led to an increase in SNR of greaterthan 14 dB.

FIG. 4 is an example of a simple emitted and received ultrasound pulsewaveform that is used, for example, in the precision arc scannerdescribed above which uses a single element transducer such as shown inFIG. 2a taken from “Ultrasonography of the Eye and Orbit”, SecondEdition, Coleman et al, published by Lippincott Williams & Wilkins,2006.

FIG. 5 shows examples of several emitted coded excitation ultrasoundpulse waveforms. This figure was taken from “Use of Modulated ExcitationSignals in Medical Ultrasound. Part I: Basic Concepts and ExpectedBenefits”, Misaridis and Jensen, IEEE Transactions on Ultrasonics,Ferroelectrics, and Frequency Control, vol. 52, no. 2, February 2005.

Tissue Harmonic Imaging

Tissue harmonic imaging exploits non-linear propagation of ultrasoundthrough body tissues. The high pressure portion of the wave travelsfaster than low pressure resulting in distortion of the shape of thewave. This change in waveform leads to generation of harmonics(multiples of the fundamental or transmitted frequency) from the tissue.Typically, the second harmonic is used to produce the image as thesubsequent harmonics are of decreasing amplitude and hence insufficientto generate a proper image. These harmonic waves that are generatedwithin the tissue, increase with depth to a point of maximum intensityand then decrease with further depth due to attenuation. Hence themaximum intensity is achieved at an optimum depth below the surface.Advantages over conventional ultrasound include: decreased reverberationand side lobe artifacts; increased axial and lateral resolution;increased signal-to-noise ratio; and improved resolution in patientswith large body habitus.

Tissue harmonic ultrasound imaging has been accepted as one of thestandard imaging modalities in many applications since its introductionto medical ultrasound imaging in the 1990s. Especially in cardiac andabdominal studies, tissue harmonic imaging is very often used fordiagnostics along with fundamental imaging. By utilizing the secondharmonic component of the received signal, images can be improved byreducing near field reverberation, decreasing phase aberration error,and improving border delineation.

Ultrasound tissue harmonic imaging utilizing nonlinear distortion of thetransmitted frequencies within the body is useful for producing asharper, higher-contrast ultrasound image than that of the fundamentalfrequency. Due to its improved conspicuity (the property of beingclearly discernible) and border definition, tissue harmonic imaging hasbeen widely used for detecting subtle lesions in, for example, thethyroid and breast, and visualizing technically-challenging patientswith high body mass index. However, compared to conventional ultrasoundimaging, tissue harmonic imaging suffers from the low signal-to-noiseratio, resulting in limited penetration depth. The signal-to-noise ratioin tissue harmonic imaging can be substantially increased by utilizingcoded excitation techniques, such as described previously in thisdisclosure. In coded tissue harmonic imaging, similar to conventionalcoded excitation, specially-encoded ultrasound signals (for example,Barker, Golay and chirp) are transmitted, and then back-scatteredreceive signals containing fundamental and harmonic frequencies areselectively decoded via pulse compression.

Tissue Harmonic Imaging and Coded Excitation Together

Tissue harmonic imaging allows one to obtain medical ultrasound imageswith higher signal-to-noise ratio and higher spatial resolution. Tissueharmonic imaging and coded excitation together have been applied tomedical ultrasound imaging. Coded excitation can overcome the trade-offbetween spatial resolution and penetration, which occurs when using aconventional transmitted pulse. For example, a chirp signal isfrequently used for medical ultrasound imaging. A combination of codedexcitation and tissue harmonic imaging has been found to producesuperior ultrasound images.

As discussed in “Use of Modulated Excitation Signals in MedicalUltrasound. Part I: Basic Concepts and Expected Benefits”, Misaridis andJensen, IEEE Transactions on Ultrasonics, Ferroelectrics, and FrequencyControl, vol. 52, no. 2, February 2005, tissue harmonic imaging allowsone to obtain medical ultrasound images with higher signal-to-noiseratio and higher spatial resolution. Tissue harmonic imaging and codedexcitation applied to medical ultrasound imaging has been investigated.Coded excitation can overcome the trade-off between spatial resolutionand penetration, which occurs when using a conventional transmittedpulse. For example, a chirp signal is frequently used for medicalultrasound imaging. A combination of coded excitation and tissueharmonic imaging has been found to produce superior ultrasound images.

As discussed in “Coded Excitation for Ultrasound Tissue HarmonicImaging”, Song, Kim, Sohn, Song and Yoo. Received in revised form 18Dec. 2009 Ultrasonics journal homepage: www.elsevier.com/locate/ultras,it is shown how coded signals, when processed with a matched filter, canbe evaluated in the presence of ultrasonic attenuation using ambiguityfunctions. It is shown that if matched-filter receiver processing isused, the compressed output is not the autocorrelation function of thecode, but a cross section of the ambiguity function for a certainfrequency downshift. Therefore, the AF of the transmitted waveform oughtto have desired properties in the entire delay-frequency shift plane.The criteria of selecting the appropriate coded waveforms and receiverprocessing filters have been discussed in detail. One of the mainresults is the conclusion that linear FM signals have the best and mostrobust features for ultrasound imaging. Other coded signals such asnonlinear FM and binary complementary Golay codes also have beenconsidered and characterized in terms of SNR and sensitivity tofrequency shifts. These results have been demonstrated. It is foundthat, in the case of linear FM signals, a SNR improvement of 12 to 18 dBcan be expected for large imaging depths of attenuating media, withoutany depth dependent filter compensation. In contrast, nonlinear FMmodulation and binary codes are shown to give a SNR improvement of only4 to 9 dB when processed with a matched filter. It was shown how thehigher demands on the codes in medical ultrasound can be met byamplitude tapering of the emitted signal and by using a mismatchedfilter during receive processing to keep temporal side lobes below 60 to100 dB.

High-Intensity Focused Ultrasound

High-intensity focused ultrasound (HIFU) is a non-invasive therapeutictechnique that uses non-ionizing ultrasonic waves to heat tissue. HIFUcan be used to increase the flow of blood or to destroy tissue, such astumors, through a number of mechanisms. The technology is similar toultrasonic imaging, although practiced at lower frequencies and higheracoustic power. Acoustic lenses may be used to achieve the necessaryintensity at the target tissue without damaging the surrounding tissue.“Systematic Review of the Efficacy and Safety of High-Intensity FocussedUltrasound for the Primary and Salvage Treatment of Prostate Cancer”, M.Warmuth, T. Johansson, P. Mad, European Urology 58 (2010) 803-815, Sep.17, 2010.

A typical HIFU transducer has a diameter of about 19 mm with a centerfrequency of about 5 MHz, a focal length of about 15 mm and a focalintensity of about 200 W/mm². Another typical HIFU transducer has adiameter of about 60 mm with a center frequency of about 1 MHz, a focallength of about 75 mm and a focal intensity of about 17 W/mm².

Present Disclosure

The present disclosure, which uses features described above, illustratestwo apparatuses for utilizing a precision ultrasound scanner to make animage of a prostate for a male patient without causing undue patientdiscomfort or health risk due to the activity of the physician or, forexample, a device such as a trans-rectal probe. A feature of eachapparatus is that the scanner positioning mechanism and scan head arecompletely immersed in water. The patient sits on the instrument withhis rectal area over an acoustically transparent window (the window mayalso be optically transparent). The ultrasound transducer is positionedas close to the underside of the window as possible prior to initiatinga sequence of scans. The ultrasound transducer is centered on the regionclosest to the patient's prostate, for example, using either ultrasoundor optical means to center on the rectum such that the ultrasound pulsesare aimed at the prostate through the perineum.

FIG. 6 illustrates the principal features of in the male perineum andthe direction 602 from which the transducer pulse is emitted. Theprostate gland 601 sits just below the bladder. The ultrasoundtransducer is moved along an arcuate or linear guide track. An arcuateguide track is preferred since the transducer can maintain anapproximately constant distance from the prostate glans 601 by moving ina curved motion 603. By imaging from below the patient through theperineum, the ultrasound emitted and reflected pulses do not passthrough any bony structures that would severely attenuate ultrasoundpulses.

The patient sits on a thin bag of acoustically transparent gel (the gelmay also be optically transparent) so that the transmission path fromthe ultrasound transducer to the prostate is substantially of the sameacoustic impedance (the gel bag conforms to the window over the scannerand to the patient's anatomy).

The male prostate is often described as the size of a walnut or golfball. The prostate gland is approximately 40 mm by 30 mm by 20 mm. Asdescribed in the present disclosure, the positioning of the patient forscanning is designed to place the ultrasound transducer approximately 50to 130 mm from the nearest surface of the prostate.

FIGS. 7A-7C are schematics of a saddle seating apparatus 705 with anultrasound scanner positioned inside the saddle apparatus. The patientis seated on saddle 704 with his rectal area over window 703. Theultrasound scanner apparatus is contained within a water-tight enclosure702 which is filled with water 715. The other instrument volume 701 isopen to the ambient air and may contain a computer, power supplies andfluidics modules.

The ultrasound scanner apparatus is comprised of a positioning mechanism712 which can be moved vertically (along the z-axis) as well as in bothlateral directions (x and y-axes) on slider 713. The ultrasound scannerapparatus is also comprised of a scan head which is further comprised ofeither or both a linear guide track 711, an arcuate guide track 710 onwhich the ultrasound transducer and its carriage 714 moves as discussedabove. The ultrasound transducer can be a single element needle probe,an annular array probe, and/or a linear transducer array. The scanningapparatus can also include a video camera (not shown) that provides anoptical image of the outside of the body part being scanned by theultrasound probe. This can enable a healthcare professional to moreaccurately position the ultrasound transducer relative to the target tobe imaged. The positioning mechanism may able to tilt. Tilting meanschanging the tilt angle of the positioner mechanism and scan head byrotating about the x-axis in the y-z plane. The arcuate guide track isaligned with the x-axis such that the transducer carriage moves back andforth in an arc aligned with the x-axis. A linear guide track would alsobe aligned with the x-axis such that the transducer carriage moves backand forth parallel to the x-axis.

FIGS. 8A-8C are schematics of a bowl seating apparatus with anultrasound scanner 803 inside. Functionally, this apparatus is similarto the apparatus of FIGS. 7A-7C. Functionally, this apparatus is similarto the apparatus of FIGS. 7A-7C. FIGS. 8A-8C are schematics of a saddleseating apparatus 814 with an ultrasound scanner positioned inside thesaddle apparatus. The patient is seated on saddle 804 with his rectalarea over window 803. The ultrasound scanner apparatus is containedwithin a water-tight enclosure 802 which is filled with water 815. Theother instrument volume 801 is open to the ambient air and may contain acomputer, power supplies and fluidics modules.

The transparent window 703 or 803 can be detachable window and isconnected to and embedded in the saddle of the scanning instrumentcontainer. The window is typically made from a material that cantransmit optical and acoustic energy. The window may be round,elliptical or square with rounded corners such that the window can allowthe scanner to scan the selected body part of the patient.

The ultrasound scanner apparatus is comprised of a positioning mechanism812 which can be moved vertically (along the z-axis) as well as in bothlateral directions (x and y-axes) on slider 813. The ultrasound scannerapparatus is also comprised of a scan head which is further comprised ofeither or both a linear guide track 811, an arcuate guide track 810 onwhich the ultrasound transducer and its carriage 814 moves as discussedabove.

As noted, the patient sits on a thin bag (not shown) of acousticallytransparent gel (the gel may also be optically transparent) so that thetransmission path from the ultrasound transducer to the prostate issubstantially of the same acoustic impedance (the gel bag conforms tothe window over the scanner and to the patient's anatomy). The thin bagis positioned between the seated patient (who is seated on the saddle704 or 804) and the acoustically transparent window 703 or 803 andconforms to the detachable window in the saddle and to the body partbeing scanned by the ultrasound probe to form the continuous acoustictransmission path to and from the target feature of the patient. Thedisposable bag of gel is typically placed over the window, and thepatient commonly sits on the bag so that the gel is in contact with thewindow and with the patient's body. Alternately, the disposable anddeformable container could, for example, be a pair of shorts with thedisposable and deformable container of clear gel sewn into the crotcharea of the shorts.

As will be appreciated, the saddle 704 or 804, in other embodiments, canbe bowl-shaped to act as a shallow reservoir for water in which thepatent is seated. In this embodiment, no gel is required. A disadvantageof this approach is that the water will need to be removed by a pump andattached piping or by a stop cock with gravity flow through piping aftereach patient is imaged. The thin bag of acoustically transparent gel, onthe other hand, can simply be removed and discarded by a health careprofessional after each patient is imaged.

The scanning instrument container formed by a saddle can comprisestirrups (not shown) for the patient's feet and handle bars (not shown)for the patient's hands. The stirrups and handle bars can allow thepatient to lean forward to assume an optimal position for scanning andassist patients in sitting and standing.

A computer (not shown), comprising input and/or output devices, controlsthe scanning apparatus (controls the positioning mechanism, the scanhead, the transmitting and receiving of the ultrasound probe and/or themanipulation of A-scans to form a B-scan of the prostate gland) asdiscussed above.

The configuration of the scanning instrument container formed by asaddle or bowl on which the patient sits can allow the scan to beconducted upwards through the patient's perineum thereby providing ashort transmission/receiving path to the prostate while remaining anon-invasive procedure that minimizes patient discomfort and risk ofinfection. This configuration, can not only provide a continuous fluidpath of substantially similar acoustic transmission properties from theultrasound transducer to the body part being scanned but alsosubstantially minimize the distance between the ultrasound transducer tothe body part being scanned.

The frequency characteristic of the ultrasound probe and the peak powerof the transducer emissions are commonly selected so that an image ofthe prostate can be formed when the prostate is about 50 to 130millimeters from the face of the transducer element. The centerfrequency of the probe may be in the range of about 10 MHz to about 40MHz to provide the required image resolution.

The peak power output of the ultrasound probe can be within the limitsestablished by the FDA or other regulatory body. For example, aspatial-peak pulse-average intensity of 94 mW/cm2 and a spatial-peaktemporal-average intensity of 190 W/cm2 would be allowable under 2008FDA guidelines. This compares to a spatial-peak pulse-average intensityof 17 mW/cm2 and a spatial-peak temporal-average intensity of 28 W/cm2allowable under current FDA guidelines for ophthalmic imaging. Thisrepresents a six-fold increase in transducer power over allowableophthalmic imaging transducer power (a scan depth of about 6 to 7.5 mmfor anterior segment scanning of the human eye and a scan depth of about25 mm for retinal scanning of the human eye).

In operation, the scanning instrument container of the bowl seatingapparatus is filled with distilled water; the disposable and deformablecontainer of clear gel is placed on the saddle; the patient sits on thecontainer of clear gel in preparation for scanning (or the patient putson the disposable shorts and sits on the saddle or bowl); the probe iscentered on the arcuate guide track; the video camera is used toposition the ultrasound probe on the area of interest of the patient(such as by the positioner assembly moving the scan head into positionfor scanning); and scans are then made at different depths of focus andat different meridians (by rotating the arcuate guide assembly about itsbeta axis or by tilting the arcuate guide assembly). Scans may also bemade through different sections of the prostate by translating thearcuate guide assembly with the positioner mechanism.

FIGS. 9A-9F illustrate modes of positioning a scan head with respect toa patient. FIGS. 9A-9F show a series of end views of the seatingapparatus shown in FIGS. 7A-7C for example. FIGS. 9A-9C illustrate atranslational positioning of the scan head 901 with respect to thevertical centerline. This mode of scanning allows a series of imagesshowing vertical cuts through the prostate gland. Using the positioningaccuracy and resolution of the eye scanning instrument described in FIG.1, lateral scan head movements of 5 to 10 microns (0.005 to 0.01 mm) areroutinely used. Thus many closely spaced vertical cuts through theprostate gland can be made with the prostate scanning instrument movingin its translational mode. As noted previously, the prostate gland isapproximately 40 mm by 30 mm by 20 mm. For example, if desired, verticalscans can be made at a lateral spacing of every 0.01 mm over a lateralrange of about 5 to about 10 mm on either side of the verticalcenterline.

FIGS. 9D-9F illustrate a tilt positioning of the scan head 901 withrespect to the vertical centerline. This mode of scanning allows aseries of images showing cuts through the prostate gland that are at aslight angle to either side of the vertical centerline. Using thepositioning accuracy and resolution of the eye scanning instrumentdescribed in FIG. 1, angular scan head movements of 1 degree areroutinely used. Thus many closely spaced angular cuts through theprostate gland can be made with the prostate scanning instrument movingin its tilt mode. As noted previously, the prostate gland isapproximately 40 mm by 30 mm by 20 mm. For example, if desired, verticalscans can be made at an angular spacing of every 1 degree over anincluded angular range of about 10 to about 25 degrees, depending on thesize of the prostate gland and the distance from the ultrasoundtransducer to the prostate.

FIG. 10 illustrates the co-ordinate system used by the scanning devicesof the present disclosure. As discussed in FIG. 1, the scanning deviceis comprised of a scan head positioning device of which only a portion1001 is shown in FIG. 10 and a scan head further comprising a linearguide track 1003, an arcuate guide track 1002 and a transducer carriage1004 on which an ultrasound transducer is mounted. The ultrasound beamemitted by the transducer is always aimed at the center of curvature ofthe arcuate guide track 1002.

The linear guide track 1003 can be held stationary while the transducercarriage 1004 moves back and forth along the arcuate guide track 1002 toform an arc scan. The linear guide track 1003 can move back and forthalong the x-axis to form to a linear scan. Both the arcuate and linearguide tracks can be moved to form more complex scanning motions. Thisscan head configuration and its various scanning motions are describedin detail in U.S. Pat. No. 8,317,709 which is incorporated herein byreference.

The positioner mechanism 1001 is also discussed in detail also in U.S.Pat. No. 8,317,709. The positioner mechanism can move the scan head inthe x, y and z directions as well as rotate the scan head around thez-axis through an angle beta. These motions are typically used toposition the scan head relative to the patient prior to scanning.

The positioner mechanism includes the ability to move the scan head inthe y-direction which allows types of scans described in FIGS. 9A-9C.

As illustrated in FIG. 10, the positioner mechanism can also be modifiedto include a tilting mechanism centered at the origin of the x-y-xco-ordinate system to allow the scan head to be tilted or rotated aboutthe x-axis thru an angle alpha. The ability to tilt the scan head allowstypes of scans described in FIGS. 9D-9F.

The z-axis is aligned with the axis of the positioner mechanism 1001.Positive motion along the z-axis moves the scan head towards thepatient's prostate gland. The x and y directions are in a plane normalto the z-axis. The arcuate guide track 1002 is aligned with the x-axissuch that the transducer carriage 1004 moves back and forth in the x-zplane along the arcuate guide track 1002. The motion of the linear guidetrack 1003 is back and forth along the x-axis. The beta directionrepresents rotation of the positioner mechanism and scan head around thez-axis. The angle alpha represents the tilt angle of the positionermechanism and scan head. The tilt angle is changed by rotating the scanhead about the x-axis.

FIG. 11 is a schematic of a bowl seating apparatus with an ultrasoundscanner inside and a patient 1101 in position for scanning the prostate.In a scanning operation, the patient 1101 remains immobile on the topwall 1104 of the enclosure as shown, for example in the bowl apparatusof FIG. 11. Since the lower end of the positioning mechanism 1106 isfixed with respect to the support surface 1102, the lower end of thepositioning mechanism 1106 is also fixed with respect to the patient1101. Any prescribed movement of the top end of the positioningmechanism 1106 and any prescribed movement of the scan head 1105 isrecorded by a magnetic or optical based positioning system such asdescribed in U.S. Pat. No. 8,758,252 which is incorporated herein byreference.

An instrument volume 1103 is separate from the fluid (typicallydistilled water) in the interior volume 1107 of the enclosure. Acomputer and other equipment are contained in instrument volume 1103while the scanning apparatus (top of the positioning mechanism and scanhead) are contained in the interior volume 1107 of the enclosure.

The ability to precisely, accurately and reproducibly determine thelocation of the scan head at all times relative to the patient enablesthe system of the present disclosure to generate high resolutionultrasound images of a selected organ of a patient as long as thereflected ultrasound waveforms can be detected.

For imaging and treating a prostate, the imaging transducer and theirradiating transducer may be positioned with respect to the perineum byusing the positioning mechanism of the arc scanning device or by aseparate transducer holder positioning mechanism attached to the scanhead. For example, in FIG. 1, a transducer carriage 104 can be designedto carry both the imaging transducer and the irradiating transducer.This would allow the transducers to be positioned for imaging orirradiating by using the positioner mechanism 109 of the arc scanningdevice. Alternately, this would allow the transducers to be positionedfor imaging or irradiating by moving the transducer carriage 104 alongthe arcuate track 102 to a desired position.

An example of a separate transducer holder positioning mechanismattached to the scan head is illustrated in FIGS. 12A-12B which shows aschematic of a revolver type swept beam transducer holder positioningmechanism attached to the scan head. FIG. 12A shows a top view of theholder looking down at a 5 mm diameter imaging transducer and a 19 mmdiameter HIFU transducer. FIG. 12B show a side view of the holder 1203,the 5 mm diameter imaging transducer 1202 and a 19 mm diameter HIFUtransduce 1203. When one of the transducers is properly positioned withrespect to the target of interest, then the other transducer can berotated into this position as needed. In other words, either transducercan be positioned to be properly located and aligned to irradiate orimage the target of interest. As can be appreciated, the diameter ofimaging transducers are typically in the range of about 5 mm to about 17mm and the diameter of irradiating transducers are typically in therange of about 20 mm to about 60 mm.

Modes of Operation

In a first mode, an imaging transducer and an irradiating therapeutictransducer are mounted in a revolver type holder such as shown in FIGS.12A-12B. The imaging transducer may be rotated into position withrespect to the prostate and an image made of the prostate scanning upthrough the perineum. Then the irradiating transducer may be rotatedinto position with respect to the prostate and the prostate can also beirradiated up through the perineum. Then the imaging transducer may berotated back into position and an image made of the irradiated prostate.

The irradiating transducer required for this task is typically in therange of about 17 mm diameter to about 30 mm in diameter, typically inthe frequency range of about 5 MHz to about 20 MHz and typically has afocal length in the range of about 20 mm to about 40 mm. The imagingtransducer is typically in the range of about 4 mm diameter to about 7mm in diameter, typically in the frequency range of about 25 MHz toabout 40 MHz and typically has a focal length in the range of about 20mm to about 40 mm. The irradiating transducer would likely require itsown pulser/receiver board while the imaging transducer, which requiresmuch less power, would have a separate pulser/receiver board.

In a second mode, a single irradiating therapeutic transducer is used ina conventional holder. The irradiating transducer required is typicallyin the range of about 17 mm diameter to about 30 mm in diameter,typically in the frequency range of about 5 MHz to about 20 MHz andtypically has a focal length in the range of about 20 mm to about 40 mm.

When operating in this second mode, coded excitation and tissue harmonicimaging techniques may be used to image the irradiated tissue. Forexample, a 15 MHz irradiating transducer would produce a strong secondharmonic at about 30 MHz that could be used for imaging. As notedpreviously, tissue harmonic ultrasound imaging has been used in medicalultrasound imaging since the 1990s.

As can be appreciated, the first mode of operation can be extended toinclude coded excitation and tissue harmonic imaging techniques toproduce images at different frequencies and/or with different focallength transducers. For example, an imaging transducer and anirradiating therapeutic transducer can be mounted in a revolver typeholder. The irradiating transducer could be about a 12 MHz transducerwith a focal length of about 20 mm to about 40 mm that would produce astrong second harmonic at about 24 MHz that could be used for imaging.The imaging transducer with a focal length of about 10 mm to about 20 mmtypically operates in the range of about 25 MHz to about 40 MHz.

This combination cited in the above example could be used to irradiatethe target organ with non ionizing ultrasound while taking images of thetarget organ at 12 MHz, 24 MHz, and 40 MHz.

A number of variations and modifications of the disclosed subject mattercan be used. As will be appreciated, it would be possible to provide forsome features of the disclosure without providing others.

The present disclosure, in various embodiments, includes components,methods, processes, systems and/or apparatus substantially as depictedand described herein, including various embodiments, sub-combinations,and subsets thereof. Those of skill in the art will understand how tomake and use the present disclosure after understanding the presentdisclosure. The present disclosure, in various embodiments, includesproviding devices and processes in the absence of items not depictedand/or described herein or in various embodiments hereof, including inthe absence of such items as may have been used in previous devices orprocesses, for example for improving performance, achieving ease and\orreducing cost of implementation.

The foregoing discussion of the disclosure has been presented forpurposes of illustration and description. The foregoing is not intendedto limit the disclosure to the form or forms disclosed herein. In theforegoing Detailed Description for example, various features of thedisclosure are grouped together in one or more embodiments for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the claimed disclosurerequires more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the followingclaims are hereby incorporated into this Detailed Description, with eachclaim standing on its own as a separate preferred embodiment of thedisclosure.

Moreover, though the description of the disclosure has includeddescription of one or more embodiments and certain variations andmodifications, other variations and modifications are within the scopeof the disclosure, e.g., as may be within the skill and knowledge ofthose in the art, after understanding the present disclosure. It isintended to obtain rights which include alternative embodiments to theextent permitted, including alternate, interchangeable and/or equivalentstructures, functions, ranges or steps to those claimed, whether or notsuch alternate, interchangeable and/or equivalent structures, functions,ranges or steps are disclosed herein, and without intending to publiclydedicate any patentable subject matter.

What is claimed:
 1. A system for treating and imaging a body part of apatient, comprising: a housing defining an enclosed volume, wherein theenclosed volume is at least partially filled with a fluid; a transducerholder positioned in the fluid in the enclosed volume of the housing,wherein the transducer holder is movable among a plurality of positions;a first ultrasound transducer positioned on the transducer holder,wherein the first ultrasound transducer emits a first ultrasound wave ina first frequency range; a second ultrasound transducer positioned onthe transducer holder, wherein the second ultrasound transducer emits asecond ultrasound wave in a second frequency range, wherein the firstand second frequency ranges are distinct, wherein the transducer holdermoves such that one of the first or second ultrasound transducers is ina position of the plurality of positions and an orientation to emit oneof the first or second ultrasound waves, respectively, for forming animage of a body part of a patient; and wherein the transducer holdermoves such that another one of the first or second ultrasoundtransducers is in the position of the plurality of positions and theorientation to transmit another one of the first or second ultrasoundwaves, respectively, to treat the body part of a patient.
 2. The systemof claim 1, further comprising: an acoustically-transparent window on asurface of the housing, wherein one of the first or second ultrasoundtransducer emits one of the first or second ultrasound waves,respectively, through the acoustically-transparent window and into thebody part of the patient.
 3. The system of claim 1, wherein the firstfrequency range is between approximately 5 MHz and 20 MHz, and thesecond frequency range is between approximately 25 MHz and 40 MHz. 4.The system of claim 1, wherein a focal length of the first ultrasoundtransducer is between approximately 20 mm and 40 mm, and a focal lengthof the second ultrasound transducer is between approximately 12 mm and40 mm; wherein the focal length of the first ultrasound transducer isdistinct from the focal length of the second ultrasound transducer. 5.The system of claim 1, wherein, when the first ultrasound transducer isin an emission position, the first ultrasound transducer emits the firstultrasound wave at a first frequency in the first frequency range, andthe first ultrasound transducer receives both the first ultrasound waveat the first frequency and a harmonic wave at a harmonic frequency thatis approximately twice the frequency of the first frequency.
 6. Thesystem of claim 5, wherein, when the second ultrasound transducer is inthe emission position, the second ultrasound transducer emits the secondultrasound wave at a second frequency in the second frequency range, andthe second frequency is greater than both the first and harmonicfrequencies.
 7. The system of claim 1, wherein the transducer holder isrotatable about an axis and has a surface that is orientatedsubstantially perpendicular to the axis, wherein the first and secondultrasound transducers are positioned on the surface of the transducerholder, and wherein the transducer holder rotates such that one of thefirst or second ultrasound transducers is in an emission position. 8.The system of claim 1, further comprising: an arcuate track, wherein thetransducer holder moves along the arcuate track such that one of thefirst or second ultrasound transducers is in an emission position. 9.The system of claim 1, wherein forming the image of the body part isenhanced by using at least one of tissue harmonic imaging and codedexcitation techniques.
 10. A method for treating and imaging a body partof a patient, comprising: providing a housing with anacoustically-transparent window on a surface of the housing, wherein thehousing is at least partially filled with a fluid; providing a firstultrasound transducer and a second ultrasound transducer in the fluid inthe housing, wherein the first ultrasound transducer emits a firstultrasound wave in a first frequency range, the second ultrasoundtransducer emits a second ultrasound wave in a second frequency range,and the first and second frequency ranges are distinct; positioning apatient on the housing with a body part positioned over theacoustically-transparent window; emitting the first ultrasound wave fromthe first ultrasound transducer, at a position and an orientation toimage the body part of the patient; emitting the second ultrasound wavefrom the second ultrasound transducer at a same position and a sameorientation as used in emitting the first ultrasound wave to treat thebody part of the patient; and emitting the first ultrasound wave fromthe first ultrasound transducer to re-image the body part of thepatient.
 11. The method of claim 10, wherein treating the body part ofthe patient comprises at least one of heating or moving the body part ofthe patient.
 12. The method of claim 10, further comprising: providingthe first and second ultrasound transducers on a transducer holder thatrotates about an axis, wherein the transducer holder rotates such thatone of the first or second ultrasound transducers is in an emissionposition to emit one of the first or second ultrasound waves,respectively, through the acoustically-transparent window and into thebody part of the patient.
 13. The method of claim 12, furthercomprising: rotating the transducer holder such that the secondultrasound transducer is in the emission position to emit the secondultrasound wave and treat the body part of the patient; and rotating thetransducer holder such that the first ultrasound transducer is in theemission position to emit the first ultrasound wave and re-image thebody part of the patient.
 14. The method of claim 10, furthercomprising: providing the first and second ultrasound transducers on atransducer holder that moves along an arcuate track; moving thetransducer holder to a position on the arcuate track where the firstultrasound transducer is in an emission position to emit one of thefirst ultrasound wave through the acoustically-transparent window andinto the body part of the patient; and moving the transducer holder tothe position on the arcuate track where the second ultrasound transduceris in the emission position to emit one of the first ultrasound wavethrough the acoustically-transparent window and into the body part ofthe patient.
 15. A system for treating and imaging a body part of apatient, comprising: a housing defining an enclosed volume, wherein theenclosed volume is at least partially filled with a fluid; anacoustically-transparent window on a surface of the housing; atransducer holder positioned in the fluid in the enclosed volume of thehousing; a first ultrasound transducer positioned on the transducerholder, wherein the first ultrasound transducer emits a first ultrasoundwave at a first frequency in a first frequency range at a commonposition and a common orientation through the acoustically-transparentwindow and into a body part of a patient to image the body part, and thefirst ultrasound transducer receives a harmonic wave at a harmonicfrequency that is approximately twice the frequency of the firstfrequency; and a second ultrasound transducer position on the transducerholder, wherein the second ultrasound transducer emits a secondultrasound wave at a second frequency in a second frequency range at thecommon position and the common orientation through theacoustically-transparent window and into the body part of the patient totreat the body part, and wherein the first and second frequency rangesare distinct, and the second frequency is greater than both the firstand harmonic frequencies.
 16. The system of claim 15, wherein thetransducer holder rotates such that one of the first or secondultrasound transducers is in an emission position to emit one of thefirst or second ultrasound waves, respectively, into a body part of apatient.
 17. The system of claim 15, wherein a focal length of the firstultrasound transducer is between approximately 20 mm and 40 mm, and afocal length of the second ultrasound transducer is betweenapproximately 12 mm and 40 mm; wherein the focal length of the firstultrasound transducer is distinct from the focal length of the secondultrasound transducer.
 18. The system of claim 15, further comprising:an arcuate track, wherein the transducer holder moves along the arcuatetrack such that one of the first or second ultrasound transducers is inan emission position to emit one of the first or second ultrasoundwaves, respectively, into a body part of a patient.
 19. The system ofclaim 18, further comprising: a linear track, wherein the arcuate trackmoves along a longitudinal length of the linear track.
 20. The system ofclaim 19, further comprising: a positioning mechanism interconnected tothe linear track, wherein the positioning mechanism moves the lineartrack in at least a first horizontal direction, a second horizontaldirection, and a vertical direction.